Depending on your perspective, free-to-play games might either be the best or worst thing to happen to the mobile platform – but whatever your take, it's hard to deny that the approach comes with notable compromises. Dead Trigger 2 is a fairly engrossing first-person shooter with a lot to offer in regards to comfortable controls and enjoyable blood-spattered gameplay, but you'll quickly find yourself sitting around doing nothing in order to avoid throwing money into the works.

Backyard Monsters: Unleashed expertly adapts Kixeye’s popular Facebook game for iOS, putting you in charge of a horde of deadly fiends as they build a mighty fortress and wage war on neighboring clans. The beasts are on the scary side of cute, morphing sweet and colorful character designs into something out of a nightmare — which rather adheres to their particular brand of destruction.

Confused demonyms notwithstanding, Romans from Mars is a fairly straightforward iOS offering from Sidekick Games: waves of green-skinned centurions are attacking your ramparts and you, a lone ballista operator, are tasked with holding them off. The Roman deity Jupiter supplies intermittent spells — an earthquake here, a lightning bolt there — but the bulk of Romans from Mars consists of launching huge arrows as quickly and accurately as possible against increasingly complex hordes of aliens. Unfortunately, it devolves into mindless tapping, while the free-to-play approach makes upgrades prohibitively expensive before long.

With a laser pistol in one hand and a glowing sword in the other, charging through long corridors filled with killer robots, oozing slime creatures, and alien freaks sounds like a good time. It is — at least to an extent — in Echo Prime. This sci-fi brawler from Robot Entertainment (Hero Academy) is a high-energy tap-fest that balances smart controls and formidable challenge. The satisfaction that comes from cleaving through droves of foes in a successful run dampens during longer play sessions, however, due to intense repetition that'll leave your wrists aching.

Tweetbot 3 embraces everything good about iOS 7. Where many of our favorite apps have undergone simple facelifts to align with the new, lighter style, Tapbots understands that iOS 7 is more than the sum of its fonts and colors. As a result, Tweetbot's interface is more alive than ever before, with rich transparencies and playful transitions that create a full and immersive experience. It starts with your timeline – the background and navigation bars have been completely bleached, with the only blasts of color coming from the blue links and icon accents, plus the new circular avatars.

It’s entirely possible to overlook Even Up. In an app marketplace hellbent on grabbing your attention with busy free-to-play arcade distractions and Helvetica-and-clean-lines brainteasers, Even Up is so unassuming you might mistake it for a simplified Sudoku board. Seemingly taking its design cues from picture slider puzzles, solving each grid requires combining all numbered tiles on top of each other in sequential order until the screen is clear. You can push any numbered tile to a matching one on the grid as long as its path is clear – from there the combined tile’s number will be one higher than whatever it was originally.

Rosetta Stone’s products immerse you in the language you are learning with its innovative teaching method and lessons that force you to think like a native speaker. Rosetta Stone Arcade Academy, a free-to-play iOS educational game, attempts to build on the foundation of the computer-based language courses by introducing some gaming components as it teaches you the basics of Spanish. The result, unfortunately, is a frustrating experience that often distracts more than it enlivens the process of learning.

Camera Plus 3.0 — not to be confused with the similarly named Camera+ — is unique among third-party camera apps. Rather than outnumber competitors with filters and effects, developer Global Delight instead focuses on improving the actual process of taking pictures, while still letting you easily enhance those already on your device. Indeed, the only filter or effect gimmick to be found here is “Pix’d,” which intelligently and automatically enhances new or existing images with just a tap – and does quite a nice job, we might add.

Apps like Mailbox and Dispatch do a fantastic job of keeping our messages moving, but there's still a danger that we could forget an important email that's been tucked out of view. Skimbox addresses such concerns with a smarter approach to email filtering. It breaks your inbox into two parts: Mainbox, reserved for important messages, and Skimbox, which contains the rest of the emails sitting in your inbox. A fairly intelligent algorithm automatically sorts messages it deems important, learning from what you read and who you reply to.

CSR Racing was an unconventional entry for the racing genre, seeing as it included very little actual racing. Instead of steering around obstacles, you were tasked with dragging down a straight stretch of road, with timed control prompts like gearshifts used to influence your performance. Still, it became a massive free-to-play hit, spawning numerous copycats along the way. Follow-up CSR Classics offers much of the same tone as the original affair, though with the added element of classic hotrods to appeal to the gear head in us all.